i just have to say that if you changed out valves four times in alittle over a year either you got a lemon, bad valve job, or you need to look at your riding technique (stay off the rev-limiter) these four strokes shouldnt take half the maintenance some of the guys are talking about.
most of this extra work is because most these guys jump off a 2-stroke and onto a 4-stroke. you shouldnt ride the two bikes the same, you dont have to rev a 4-stroke to an inch of its life all the time, they have lots of power everywhere not just at wide open. :yikes: